During the course of my research in asymmetric organocatalysis, inversion enantioselectivity was observed aldol reactions acetone with different aldehydes catalyzed by amphiphilic proline derivatives aqueous media varying only achiral components. It not possible to explain explored dual stereocontrol existing models, therefore I proposed a new mechanism for l-amino acid and explained phenomenon...

For the class A β-lactamase SHV-1, the kinetic and mechanistic properties of the clinically used inhibitor sulbactam are compared with the sulbactam analog substituted in its 6β position by a CH2OH group (6β-(hydroxymethyl)penicillanic acid). The 6β substitution improves both in vitro and microbiological inhibitory properties of sulbactam. Base hydrolysis of both compounds was studied by Raman ...

The dienylborane 2a was prepared by regioselective alkyne hydroboration of the conjugated enyne 1a with Piers' borane [HB(C6F5)2]. Its reaction with a series of acetophenone derived enamines 3 resulted in the formation of the strong enamine β-carbon adduct with the borane Lewis acid (4). In contrast B-C adduct formation between the dienylborane 2a and a series of much more bulky cyclohexanone d...

The direct insertion of nitriles into zirconocene-1-aza-1,3-diene complexes provides an efficient, chemoselective, and controllable synthesis of N-H and N-substituted pyrroles upon acidic aqueous work-up. The outcome of the reaction (that is, the formation of N-H or N-substituted pyrroles) results from the different cyclization patterns, which depend on the relative stability and reactivity of ...

The mechanism of a recently reported aldehyde alpha-oxyamination reaction has been studied using a combination of kinetic, spectrometric, and spectrophotometric techniques. Most crucially, the use of a validated cyclopropane-based radical-clock substrate has demonstrated that carbon-oxygen bond formation occurs predominantly through an enamine activation manifold. The mechanistic details report...

We have demonstrated that the catalytic and enantioselective vinylcyclopropane-cyclopentene rearrangement can be carried out on (vinylcyclopropyl)acetaldehydes through activation via enamine intermediates. The reaction makes use of racemic starting materials that, upon ring opening facilitated by generation a donor-acceptor cyclopropane, deliver an acyclic iminium ion/dienolate intermediate in ...

N-Allyltetramethylpiperidine is readily isomerized to the corresponding enamine by treatment with catalytic amounts of B(C6F5)3. It adds HB(C6F5)2 at the nucleophilic enamine carbon atom to form a C/B Lewis adduct. This reacts with two molar equivalents of carbon monoxide by selective head to tail coupling to give a five-membered C2O2B heterocycle. In contrast the enamine/HB(C6F5)2 Lewis pair r...

N-Allyltetramethylpiperidine is readily isomerized to the corresponding enamine by treatment with catalytic amounts of B(C6F5)3. It adds HB(C6F5)2 at the nucleophilic enamine carbon atom to form a C/B Lewis adduct. This reacts with two molar equivalents of carbon monoxide by selective head to tail coupling to give a five-membered C2O2B heterocycle. In contrast the enamine/HB(C6F5)2 Lewis pair r...

Class I fructose-1,6-bisphosphate aldolases catalyze the interconversion between the enamine and iminium covalent enzymatic intermediates by stereospecific exchange of the pro(S) proton of the dihydroxyacetone-phosphate C3 carbon, an obligatory reaction step during substrate cleavage. To investigate the mechanism of stereospecific proton exchange, high resolution crystal structures of native an...